This invention relates to an improved process and apparatus for continuously polymerizing ethene both at high pressures and temperatures in a cylindrical autoclave in the presence of an initiator. The ethene is mixed with the contents of the autoclave by feeding the ethene into the autoclave at a high velocity. The polymerization is usually carried out at a pressure of about 500 to 10.000 at and a temperature of about 100.degree. to 400.degree.C.
As described in U.S. Pat. No. 3,692,763, it is known to pass ethene into an autoclave through a feed tube having a restriction therein, such that the pressure of the ethene within the tube is increased and thus the velocity of the ethene is increased as it exists the tube. As a result, ethene which passes tangentially into the autoclave collides, at a high velocity, with the material and mass contained within the autoclave. As a result, the internal mass together with the inflowing ethene is constantly maintained in a whirling, mixing motion due to the transfer of impulses from the inflowing ethene.
The use of such so-called propulsive jets produces a current in the autoclave comparable to conventional autoclaves where mixing is accomplished by means of a stirrer.
Advantages of such a jet method over mechanical mixing are:
A. No maintenance, dismantling, alignment, and assembly of the stirrer is required. Nor is it necessary to replace worn-out bearings, when trouble occurs. As a result, production losses due to maintenance work are lower. PA1 B. No investment costs in stirring equipment (motor, stirrer, etc.), which can amount to about 30 % of the total reactor cost. PA1 C. Enlargement of the effective reactor volume by 10 to 15 %. PA1 D. Elimination of possible hazard due to overheating of a bearing which might give rise to spontaneous decomposition of the ethene. PA1 E. No contamination of the product by metal particles produced by wear of the bearings.
It is the primary object of this invention to improve the mixing of ethene with the autoclave contents.
It is a further object of the present invention to reduce the energy required for polymerizing ethene by suitably arranging the feed nozzles.